Quite right John, very interesting shots on the facebook link you sent. Will certainly try and get to the Museum of Lincolnshire Life in September to have a look at the couple of displays they have (hopefully, since this posting was 2 or 3 years back) Regrettably Sri Lanka, Spain, Aussie outback plus some of the other places where Sentinels are shown are not on my travel plans this year.

Also Hatfield Shed and Richard; I had no idea when starting this thread that there was so much to Sentinels generally, I only associated Sentinels with steam railcars - huge leaning curve.

Frizinghall Models have come back to me with the comment 'the only sound file currently available is the YouChoos LNER steam Sentinel shunter and it is recorded from the GWR steam railmotor with LNER whistles without the geared effect. Therefore it's only an approximation and currently you can't listen to the project on their website'.

They also note 'Soundtrax do (or did) a thin PCB with several synchronising disks on it, one of which is for 8 cylinder locos'.

Being totally non-technical and stuck down here south of the equator I am unlikely to be able to investigate 'in situ' as it were, do either Frizinghall's YouChoos or Soundtrax suggestions sound like an acceptably accurate option?